Radiation induced darkening of leuko dyes has been used as the basis of various dosimeters for measurements of high nuclear radiation doses in the range of 10.sup.3 to 10.sup.7 rads. This is because leuko dyes are colorless dyes which change color when exposed to ionizing radiation. Though the use of leuko dyes has been good for scientific dosimetry, the leuko dyes have not been used for personnel dosimetry where the range of interest is 0 to 1000 rads.